Polyacetal polymers, which are commonly referred to as polyoxymethylenes (POMs), have become established as exceptionally useful engineering materials in a variety of applications. POMs for instance, are widely used in constructing molded parts, such as parts for use in the automotive industry and the electrical industry. POMs, for instance, have excellent mechanical property, fatigue resistance, abrasion resistance, chemical resistance, and moldability.
Although polyacetal resins possess many useful properties, the polymers have a tendency to degrade when heated and are inherently unstable in an oxidative atmosphere or in an acidic or alkaline environment. In particular, polyacetal resins have a tendency to emit formaldehyde during processing and after the polymer has been molded into a part. Formaldehyde is not only a contaminant, but can also adversely affect metallic components that may be placed in association with the polymer. For example, formaldehyde readily oxidizes to formic acid which can corrode metals or cause discoloration.
In view of the above, those skilled in the art have suggested using various stabilizers in molding compositions containing polyacetal polymers in order to suppress degradation. For example, various stabilizers are disclosed in JP-08208946, in Japanese Patent Application Kokai No. 60-90,250, in Japanese Patent Application Kokai No. 7-173,368 and in Japanese Patent Application No. 7-331,028. Various stabilizers that have been proposed in the past include, for instance, nitrogen containing compounds such as a dicyandiamide or an amino-substituted triazine compound.
Generally, the use of stabilizers described above such as melamines, benzoguanamine or hydrazines have been somewhat successful in achieving low formaldehyde emission performance. In some applications, however, it is desirable to produce articles and parts from polyacetal polymers that have a low gloss or matt finish. Consequently, in these embodiments, a low gloss additive may be added to the polymer composition. Adding a low gloss additive to reduce surface gloss, however, can significantly increase formaldehyde emissions even when the above stabilizers are present. Thus, further improvements are still needed in reducing formaldehyde emissions in polymer formulations containing polyacetal resins. In particular, a need exists for a polymer composition containing a polyacetal resin that produces low gloss products at reduced formaldehyde emissions.